The present invention relates to a semiconductor manufacturing apparatus for manufacturing a semiconductor device, particularly relates to dry etching technology for etching semiconductor material using plasma.
The dry etching technology is technique for etching semiconductor material such as silicon and a silicon oxide film by plasma using a minute contour patterned by resist material for a mask by lithography using light or an electron beam so as to acquire a desired form, and is one of indispensable techniques in a semiconductor manufacturing process. In dry etching, a part except a masked part of the surface of a sample is etched by pumping material gas into a vacuum chamber provided with exhaust means, turning the material gas into plasma by an electromagnetic wave and exposing a sample to it and a desired form is acquired. High frequency voltage different from high frequency voltage for producing plasma is applied to the sample, the efficiency of etching is enhanced, and the perpendicularity of the form of the sample is acquired by accelerating ions in plasma by the high frequency voltage and making them incident upon the surface of the sample.
In a conventional type dry etching apparatus, in etching, plasma potential is made higher than earth potential by voltage of a frequency for discharge for producing plasma or high frequency voltage applied to a sample. Accelerated ions out of plasma are incident upon a wall of a vacuum chamber at earth potential by the rise of the plasma potential and the wall of the vacuum chamber is sputtered. When the wall of the vacuum chamber is sputtered, the material of the wall of the vacuum chamber or a compound of the materials of the wall of the vacuum chamber is splashed on the sample to be a source of contamination and a foreign matter and the manufacturing yield of the sample which is a semiconductor device is deteriorated. Besides, as the wall of the vacuum chamber is wasted by sputtering, it is required to be regularly replaced, a running cost of the dry etching apparatus is increased, and the rate of operation is deteriorated.
For a solution of the problem, a method of applying the same frequency different by 180 degrees in a phase from high frequency voltage applied to the sample to an electrode for generating discharge arranged in a position opposite to the sample is proposed (for example, refer to Japanese Patent Application Laid-Open No. 2002-184766 (patent document 1) and pp. 43 to 48 of 2003 Proceedings of International Symposium on Dry Process (non-patent document 1)). As the opposite electrode is turned at negative potential in a positive-voltage cycle of the high frequency voltage applied to the sample by applying the high frequency voltage different by 180 degrees in a phase from the high frequency voltage applied to the sample to the electrode for generating discharge, the rise of plasma potential is suppressed and the sputtering of the wall of the vacuum chamber is suppressed.
Besides, a method of providing a filter to the electrode for generating discharge to make the high frequency voltage applied to the sample efficiently flow from the electrode for generating discharge to the earth is proposed (for example, refer to Japanese Patent Application Laid-Open No. 2002-43286 (patent document 2)).
Besides, a method of inserting a filter having the length of a wavelength equivalent to ¼ of a frequency for discharge into a sample mounting electrode is proposed (for example, refer to Japanese Patent Application Laid-Open No. 2002-16045 (patent document 3)).